We propose to continue ongoing studies of the immunopathologic mechanisms responible for glomerulonephritis and tubulo-interstitial nephritis in man. The studies are designed to identify the occurrence, incidence, clinical-pathologic presentation and course, etiologic and initiating factors, and the basic immunopathologic features of the mechanisms themselves by study of tissue and serum from nephritic patients. The studies in man are coupled with evaluation of relevant animal models of immunologic renal disease. Areas of study to be emphasized are as follows: Identify etiologic antigens in immune complex glomerulonephritis, detect and monitor circulating immune complexes, determine the nature and physiology of antigens and events leading to anti-basement membrane antibody responses, utilize radioimmunoassay techniques to monitor the anti-basement membrane antibody response and its clinical-therapeutic correlates, search for the mechanisms responsible for the development of recurrent nephritogenic processes in renal transplants, explore the nephritogenic role of chronic complement activation in the initiation or perpetuation of glomerular or tubulo-interstitial renal disease, and work out the role of immune complexes and anti-basement membrane antibodies in tubulo-interstitial renal injury.